"Long before it's in the papers"
February 23, 2016


Warming may be raising seas faster than anytime in at least 2,800 years

Feb. 23, 2016
Courtesy of PNAS
and World Science staff

Glob­al warm­ing is probably al­ready fuel­ing a sea lev­el rise that’s faster than at any time in at least 2,800 years, sci­en­tists are re­port­ing.

Pub­lish­ing their find­ings this week in the jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces, re­search­ers re­port an es­ti­mate of glob­al sea-lev­el changes over the past 3,000 years. 

The investigators, Rob­ert Kopp of Rut­gers Un­ivers­ity in Pis­cat­away, N.J. and col­leagues, es­ti­mated glob­al sea-lev­el changes over the pe­ri­od us­ing re­gion­al sea-lev­el re­con­struc­tions from 24 loca­t­ions.

Be­tween the years 0 and 1900 A.D., glob­al sea lev­el varia­t­ion was likely be­tween 7 cm and 11 cm, or up to about four inches. Be­tween 1000 and 1400, the lev­els de­creased an av­er­age of one fifth of a mil­li­me­ter per year, or less than a thou­sandth of an inch, co­in­cid­ing with a slight glob­al tempe­rature drop, they es­ti­mated. 

They al­so con­clud­ed based on their re­con­struc­tion that it is ex­tremely likely that the sea-lev­el rise in the 20th cen­tu­ry—14 cm, or 5.5 inch­es—was faster than dur­ing any pre­vi­ous cen­tu­ry since at least 800 B.C.

Af­ter cre­at­ing a mod­el to re­late the rate of sea-lev­el change to the av­er­age tempe­rature, the re­search­ers es­ti­mated the hu­man con­tri­bu­tion to 20th-cen­tu­ry sea-lev­el rise, con­clud­ing that it probably ac­counts for more than half of that in­crease.

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Global warming is already contributing to a sea level rise that’s levels faster than at any time in at least 2,800 years, scientists are reporting. Publishing their findings this week in the journal pnas, researchers report an estimate of global sea-level changes throughout since the year 0 A.D. Robert Kopp of Rutgers University in Piscataway, N.J. and colleagues estimated global sea-level changes over the period using regional sea-level reconstructions from 24 locations. Between the years 0 and 1900, global sea level variation was likely between 7 cm and 11 cm, or up to about four inches. Between 1000 and 1400, the levels decreased an average of one fifth of a millimeter per year, or less than a thousandth of an inch, coinciding with a slight global temperature drop, they estimated. They also concluded based on their reconstruction that it is extremely likely that the sea-level rise in the 20th century—14 cm, or 5.5 inches—was faster than during any previous century since at least 800 B.C. After creating a model to relate the rate of sea-level change to the average temperature, the researchers estimated the human contribution to 20th-century sea-level rise, concluding that it probably accounts for more than half of that increase. 2,800 years